An image forming apparatus executes printing in response to a print request. The image forming apparatus forms an image on a conveyed paper sheet and discharges the paper sheet on which the image is formed. For example, the image forming apparatus forms an image on the paper sheet by forming a toner image on the paper and fixing the toner image with a fixing roller having a high temperature.
A power conversion circuit used in the image forming apparatus generates a pulsated positive voltage by full-wave rectifying a commercial power input which is an AC power supply with a diode bridge. Further, the power conversion circuit generates high frequency current from the pulsated positive voltage with a half bridge inverter and a full bridge inverter connected to the diode bridge. In the power conversion circuit, the high frequency current flows to a coil to generate an induced current (eddy current) in a load by the magnetic field generated in the coil. As a result, heat is generated in the load. The fixing roller is heated to a high temperature by the heat generated in the load.
In Japanese Unexamined Patent Application Publication No. 2007-080752, an induction heating cooking device for detecting a state of the load to select constitution of an inverter circuit suitable to heating and set an inverter drive condition is described.